Swift 3 / Xcode 8 Upgrade - 100's of DerivedData files missing from working copy errors

Question

I have just upgraded to the latest Beta version of XCode and Swift but after using the converter my app project now has over 200 build time yellow errors all stating /\"projectD

Answer 1

I think I've resolved the issue now by deleting all instances of my DerivedData folder and following crashoverride777's instructions. I also had to change my DerivedData option from relative to Custom which can be found in Xcode > Preferences > Locations Tab.